The present invention relates to a wireless communication system having a plurality of electronic devices that exchange encrypted data with a wireless transmission.
Conventionally, wireless communication systems typically known as a wireless LAN (Local Area Network) are in widespread use. In the wireless communication system, in order to keep secrecy of data exchanged between the electronic devices, encryption system is generally employed.
In a transmitting station, data is encrypted before transmitted using a predetermined data (which will be referred to as ciphering data) for encryption. In a receiving station which receives the thus encrypted data, the encrypted data is decoded using deciphering data. It should be noted that, when the ciphering data used for encrypting and the deciphering data used for decoding are the same, i.e., the ciphering data used for encrypting can also be used for decoding, the deciphering data is also called as the ciphering data.
As the encryption system, a public key encryption system in which the ciphering data and the deciphering data are different, and a common key encryption system in which the ciphering data and the deciphering data are the same have generally been known. It is also known that the common key encryption system requires less processing load to the communication system than the public key encryption system since the same ciphering/deciphering data is used in the transmitting and receiving stations.
In the encrypting/decoding system that does not require that the deciphering data is transmitted from the receiving station to the transmitting station, there is little chance that the deciphering data is known by other stations. Thus, in such a system, the encrypted data will hardly be decoded by other stations, and the secrecy of the data can be kept.
An example of the communication system employing the public key encrypting system is disclosed in Japanese Patent Application Provisional Publication No. HEI 10-224340. According to the system disclosed in this publication, in order to improve the secrecy of data exchanged between a wireless transmitting station and a wireless receiving station, data such as a pop table is encrypted using public key data (i.e., the ciphering data), and the encrypted data is transmitted to the receiving station. Then, in the receiving station, with use of preliminary set secret key data (i.e., deciphering data), the received data is decoded. In this system, data should be encrypted using the public key data that corresponds to the secret key data, and thus, the public key data has been transmitted from the receiving station to the transmitting station.
In the common key encrypting system, the same key data (i.e., the common key data) is used for encrypting in the transmitting station, and for decoding in the receiving station. If, in such a system, the common key data is transmitted from the receiving station to the transmitting station, it may be received by another station which is not intended by a user. It should be noted that, any station which receives the common key data, can decode the encrypted data using the same common key data, and it is hard to keep the secrecy in such a case.